Operator serviceable corona charging apparatus

ABSTRACT

A corona charging assembly for electrostatic copy machines is disclosed as having an elongated U-shaped shell and an elongated U-shaped, snap-on cover for access through a backwall opening in the shell to the corona wires for cleaning thereof. In practice, two opposed charging assemblies are employed and are readily removable from the machine by disengagement from mounting means and plug-in high voltage connections.

[ 1 Oct. 9, 1973 United States Patent 91 Hirschman 3,609,354 9/1971 Herman....................... 250/49.5 ZC 3,496,352 2/1970 250/49.5 ZC

A N O R 0 C E us AU n mm a SA RG ON TI G u ma 0C 4 U Primary Examiner-James W. Lawrence Assistant Examiner-C. E. Church Att0meyWilliam D. Soltow, Jr. et al.

[57] ABSTRACT A corona charging assembly for electrostatic copy ma- Jan. 24, 1972 [21] Appl. No.: 220,054

chines is disclosed as having an elongated U-shaped shell and an elongated U-shaped, snap-on cover for 250/495 ZC [51] Int. G03g 15/00 access hr gh a kw ll pening in the shell to the [58] Field of 250/495 ZC; 'eorona r s for ng t In pra two p- 317/262 A posed charging assemblies are employed and are readily removable from the machine by disengagement from mounting means and plug-in high voltage connections.

[56] References Cited UNITED STATES PATENTS 250/495 ZC 5 Claims, 3 Drawing Figures I PATENIED BET 9 I973 OPERATOR SERVICEABLE CORONA CHARGING APPARATUS BACKGROUND OF THE INVENTION In the direct imaging method of making copies electrostatically, paperhaving a thin coating of a photoconductive insulating material is exposed to a corona charging device for producing a uniform high voltage electrostatic charge on the coated side of the paper. The paper is then photographically imaged to dissipate the charge in the light non-image areas, with the charge being retained on the dark image areas. The imaged copy sheet is then developed with electroscopic toner particles which are electrostatically attracted to the charged surface areas of the copy paper.

The corona charging device employed in this process typically comprises a grounded 'she lland one or more corona discharge wires which are positioned contiguous to and across the path of travel of the coated copy paper. The wires are very thin and generally are charged to a potential of about 6,000 volts.

Because of the high voltage on thethin corona wires, dust and dirt are strongly attracted thereto and, when the wire becomes even partially coated by such contaminants, the charging capability of the wire is substantially diminished. The coating or partial coating of the thin wires may prevent the corona discharge from accuring. This is due to thefactthat the dirt acts as an effective insulator and also increases the diameter of the wire, which mustremain extremely thin. Further, since the charging of the photoconductor must be overall uniform, dirtor other foreign matter'oneven a part of the wire will result in streaks orbands of imageless drawn to replace the dirty wire, as set forth in US Pat.

No. 3,499,143. The problem has also been recognized in US. Pat. No. 3,339,069.

BRIEF SUMMARY OF THE INVENTION The present invention provides for easy access'to the wires of corona discharge devices by providing for their convenient and complete removability and by the provision of a readily removable cover for access through *the shell to the corona wires.

In a preferred embodiment of the invention the electrostatic charger generally comprises an elongated electrically conductive shell member forming a threesided housing for the corona discharge wire. Terminal blocks of insulative material are secured at each end of the shell and the corona discharge wire is stretched between these terminal blocks. The shell is U-shaped in cross-section and is provided with paperguide means preferably in "the form of a polymeric string strung across the open mouth of the shell to maintain the requisite spacing and prevent entryof copy paper during charging. The shell is provided with a removable electrically conductive cover foran elongated opening in the backwall of the shell. The cover can be snapped on and off the shell with a minimum of effort and is held quickly reinstalledwith a minimum of down time of the copy machine. The electrical connections are made automatically when the charging assemblies are remounted in place, and accordingly the removal and cleaning of the corona charging assemblies can be done by machine operator personnel rather than service personnel.

Accordingly it is an object ofthe invention to provide an electrostatic corona charging device for photocopy machines which accommodates ready access to the corona discharge wire for the cleaning.

Another object of the invention is to provide an electrostatic charging device which is readily removable from the photocopying machine by relatively untrained personnel.

A further object of the invention is to provide an electrostatic charging device of the above character wherein the construction is simple in design and inexpensive to manufacture.

Another object of the invention is toprovide an electrostatic charging device of the above character wherein the electrical connections are made thereto incident 0t the'physical installation thereof in the photocopy machine.

"Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the features of construction, combination of elements, and arrangement ofparts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims. 7 For a'fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing in which:

FIG. 1 is a broken side elevation view of a partial section of an'electrostatic corona charging apparatus constructed in accordance with theinvention;

FIG. 2 is a partial top view in partial section taken along lines 2-2 of FIG. 1 showing the high voltage connections to the apparatus;

FIG. 3 is a partial perspective view of the apparatus of the invention with the shell cover of the corona charging assembly partially removed.

Similar reference characters refer to similar parts throughout the several views of the drawing.

DETAILED DESCRIPTION OF THE INVENTION Referringnow to the drawing, the invention will be describedin more detail. As best seen in FIGS. 1 and 3, the electrostatic corona charging apparatus comprises upper and lower corona charging assemblies 10 and 12, respectively. The upper assembly 10 is provided with an elongated electrically conductive shell 14 which is U-shaped in cross-section. Terminal blocks 16 and 18 are secured in each end of the shell and preferably made of polymeric material. Terminal blocks 16 and 18 preferably are each provided with a lateral extension 19 terminating in deformable protrusions 20 which snap-fit about a shaft 22 to removably and pivotably mount the upper assembly in the manner more fully disclosed in the commonly assigned, copending application of Hoffman et al., Ser. No. 131,064, filed Apr. 5, l97l. Thus, assembly 10 may be pivoted upwardly on shaft 22 for removal of paper jams and the like and may be completely removed for cleaning or replacement of. the corona discharge wires 65.

Lower charging assembly 12 has a similar elongated shell 24 of U-shaped cross-section to which are secured insulative terminal blocks 26, 28. The respective shells and terminal blocks may be secured together by screws 27 of electrically insulating material such as nylon.

Shell 14 is provided with a cover 30 which is also U- shaped in cross-section and preferably snaps into mating engagement therewith by means of detents 32a, 32b in the cover and shell respectively, as best seen in FIG. 3. Similarly, the shell 24 of the lower assembly is provided with a U-shaped cover 34 which is also preferably snap fitted into mating engagement therewith. Both covers 30 and 34 are provided with a raised edge area 36 at one end to facilitate the entry of a prying tool between the cover and shell pursuant to removing the cover for access to the corona discharge wires. Preferably there is one such tool engaging area at each end of the cover. With the covers removed openings 14a and 240 formed in the shell backwalls are uncovered for access to the corona wires which extend between the terminal blocks 16, 18 and 26, 28. The wires may be readily cleaned by a suitably shaped tool introduced through the shell openings.

Both of the assemblies 10 and 12 are completely removable from and replaceable back into the copy machine by relatively untrained personnel. As seen in FIG. 2, terminal block 26 of lower assembly 12 is provided with a pair of longitudinally extending sleeves 26a and 26b which are loosely received in sockets 37a and 37b formed in an insulative mounting block 37 secured to a copier sideplate 38, thereby to mount one end of the lower charger assembly. Block 37 also mounts bifurcated spring contacts 39a extending into socket 37a for electrical contacting engagement with a spade contact 40 mounted by terminal block 26 and extending through sleeve 26a. As seen in FIG. 1, spade contact 40 is L-shaped to provide an upward extension 40a for electrically contacting engagement with a tab contact 41 mounted by and depending from terminal block 16 of upper assembly 10 when in operative relation to the lower assembly. The upper end of tab contact 41 is connected to corona wires 65. In the same manner bifurcated spring contacts 391: extend into socket 37b for engagement with a spade contact 42 carried by terminal block 26 and extending through sleeve 26b. Spade contact 42 is electrically connected to corona wires 63 of the lower assembly 12.

It is thus seen that the one end of the lower corona charging assembly shown in FIG. 2 is conveniently, removably mounted in place. It is also noted that, incident to mounting the lower assembly, high voltage connections for the charging apparatus are effected to the high voltage supply (not shown).

The other end of the lower charger assembly, as seen in FIG. 1, rests on the horizontally extending saddle portion 48a of a bracket 48 bolted, as indicated at 50, to a metal sideplate 52 of the copier. An electrically conductive, resilient clip 42 is secured at its lower end by screws 27 to terminal block 28, but in electrically contacting engagement with shell 24. A second electrically conductive, resilient clip 44 is secured by screws 27 to terminal block 18 in electrically contacting engagement with shell 14 of the upper assembly 10. Upon mounting the lower assembly, a crook 42a in spring clip 42 engages a slot 46 in bracket 48 to provide a mechanical detenting function for releasably retaining the right end of the lower assembly in place, as well as grounding shell 24 to the copier chasis. When the upper assembly 10 is pivoted downwardly to its operative position resting on top of the lower assembly, a crook 44a in clip 44 engages a second crook 42b in clip 42 to also ground shell 14 to the copier chasis and to releasably retain the upper assembly in position.

To guide copy paper successfully between the assemblies 10 and 12 and to prevent entry of copy paper into the shells in the event of a jam, the edges of the shell sidewalls are flared outwardly to provide entry and exit guide lips 54 and 56, respectively. These lips are tabbed, as at 58, to facilitate the stringing of an insulating monofilamentstrand 60 back and forth across the open side of each of the shells 14 and 24. The exit guide lips 56 are preferably covered with insulating material 64 under the polymeric string to prevent discharging of the copy paper unon exiting the charging apparatus.

In operation, when the corona wires 63, 65 become dirty and must be cleaned, the upper assembly 10 is removable by merely swinging it upwardly and snapping it off of shafts 22. The cover 30 is then removed for access through shell opening 14a along substantially the entire length of the corona wires which may then be cleaned by a wet swab or the like. Assembly 12 is then removed by grasping the upper end of clip 42 and pulling upward to lift the right end of the lower assembly from the supporting and grounding bracket 48 upon disengagement of crook 42a from slot 46 in bracket 48. With continued lifting motion, sleeves 26a and 26b slide out from sockets 37a and 37b, and the electrical connections are broken incident to complete removal of the lower assembly. The covers of shell 24 is then readily removable by engagement of a simple tool such as a screwdriver or even a coin under raised portion 36. The procedure is merely reversed to replace the upper and lower assemblies.

It will thus be seen that the objects set forth above, among those made apparent from the preceeding desc'ription, are efficiently attained and, since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. Corona charging apparatus for electrostatic copier machines, said apparatus comprising, in combination:

A. first and second corona charging assemblies each including 1. an elongated conductive shell having an open side,

2. an electrically insulative terminal block secured at each end of said shell,

3. at least one corona discharge wire extending between said terminal blocks, 4.' copy paper guide means extending across said open side, 5. means forming an elongated opening in said shell, and 6. an electrically conductive cover detachably mounted to said shell over said opening; B. a mounting block secured to the copier frame, C. engageable means carried by said mounting block and one of said terminal blocks of said first assembly for releasably mounting one end of said first assembly and for providing external high voltage connections to said corona discharge wires, D. a bracket secured to the copier frame for releasably mounting the other end of said first assembly, E. first and second electrically conductive grounding members respectively carried by said first and second assemblies for grounding said shells thereof to the copier frame, F. means releasably mounting said second assembly in opposed, contiguous relation to said first assembly, and G. a contact carried by said one terminal block of said first assembly and the opposed one of said terminal blocks of said second assembly for completing a high voltage circuit to said corona wire of said second assembly when both said assemblies are in opposed operative relation.

2. The apparatus defined in claim 1, wherein said engageable means includes a mating socket and sleeve pair with mating electrical connectors accommodated therein.

3. The apparatus defined in claim 2, wherein said first grounding member is formed havingdetent means for engaging complimentary detent means on said bracket to retain said other end of said first assembly releaseably mounted thereon and to ground said shell thereof.

4. The apparatus defined in claim 3, wherein said first and second grounding members are formed with complimentary engageable latch means for electrically connecting said grounding members in common and for releasably retaining said second assembly in opposed operative relation to said first assembly.

5. The apparatus defined in claim 1, wherein said shells and said covers, are U-shaped in cross section having backwalls and opposed sidwalls, said openings being formed in said backwalls of said shells opposite said open sides, and mating detent means provided in said side walls of said covers and said shells for snap fitting said covers to said shells. 

1. Corona charging apparatus for electrostatic copier machines, said apparatus comprising, in combination: A. first and second corona charging assemblies each including
 1. an elongated conductive shell having an open side,
 2. an electrically insulative terminal block secured at each end of said shell,
 3. at least one corona discharge wire extending between said terminal blocks,
 4. copy paper guide means extending across said open side,
 5. means forming an elongated opening in said shell, and
 6. an electrically conductive cover detachably mounted to said shell over said opening; B. a mounting block secured to the copier frame, C. engageable means carried by said mounting block and one of said terminal blocks of said first assembly for releasably mounting one end of said first assembly and for providing external high voltage connections to said corona discharge wires, D. a bracket secured to the copier frame for releasably mounting the other end of said first assembly, E. first and second electrically conductive grounding members respectively carried by said first and second assemblies for grounding said shells thereof to the copier frame, F. means releasably mounting said second assembly in opposed, contiguous relation to said first assembly, and G. a contact carried by said one terminal block of said first assembly and the opposed one of said terminal blocks of said second assembly for completing a high voltage circuit to said corona wire of said second assembly when both said assemblies are in opposed operative relation.
 2. an electrically insulative terminal block secured at each end of said shell,
 2. The apparatus defined in claim 1, wherein said engageable means includes a mating socket and sleeve pair with mating electrical connectors accommodated therein.
 3. The apparatus defined in claim 2, wherein said first grounding member is formed having detent means for engaging complimentary detent means on said bracket to retain said other end of said first assembly releaseably mounted thereon and to ground said shell thereof.
 3. at least one corona discharge wire extending between said terminal blocks,
 4. copy paper guide means extending across said open side,
 4. The apparatus defined in claim 3, wherein said first and second grounding members are formed with complimentary engageable latch means for electrically connecting said grounding members in common and for releasably retaining said second assembly in opposed operative relation to said first assembly.
 5. The apparatus defined in claim 1, wherein said shells and said covers are U-shaped in cross section having backwalls and opposed sidewalls, said openings being formed in said backwalls of said shells opposite said open sides, and mating detent means provided in said side walls of said covers and said shells for snap fitting said covers to said shells.
 5. means forming an elongated opening in said shell, and
 6. an electrically conductive cover detachably mounted to said shell over said opening; B. a mounting block secured to the copier frame, C. engageable means carried by said mounting block and one of said terminal blocks of said first assembly for releasably mounting one end of said first assembly and for providing external high voltage connections to said corona discharge wires, D. a bracket secured to the copier frame for releasably mounting the other end of said first assembly, E. first and second electrically conductive grounding members respectively carried by said first and second assemblies for grounding said shells thereof to the copier frame, F. means releasably mounting said second assembly in opposed, contiguous relation to said first assembly, and G. a contact carried by said one terminal block of said first assembly and the opposed one of said terminal blocks of said second assembly for completing a high voltage circuit to said corona wire of said second assembly when both said assemblies are in opposed operative relation. 